In recent years, an xDSL modem as represented by the ADSL modem has become popular. The xDSL modem has been used in various ways depending on the services of ISP (Internet Service Providers). In many cases, the xDSL modem has been used for providing always on access type services. Therefore, the xDSL modem operates to place the priority to the connection of a communication line during all times. For example, the xDSL modem has been designed to operate with priority to try connecting a personal computer to a communication line at the time when the power supply to the personal computer is turned on or immediately after the line has been disconnected.
At present, a reduction in power consumption of various machines has been strongly required from the viewpoint of global warming prevention. This situation is not an exception in computers and communication equipment. From this viewpoint, the xDSL technology has had a problem of a rise in power consumption as this technique has been considered based on always on access. Notwithstanding this requirement, a focus has mainly been placed on the increase in transmission speed to a higher speed and on a noise reduction, with no sufficient care paid to the power saving. From the above situation, at present, there has been strongly demanded for a technique of reducing power consumption without losing the own characteristics of the xDSL like the high-speed transmission and always on access.
Specifically, a portable information processing equipment like a notebook-type computer is connected to a communication line only sometimes, as it is carried based on the needs. When the notebook-type computer establishes a communication path in this unconnected status, this leads to a waste of power consumption, and this is not suitable from the viewpoint of global warming prevention.
Further, in the case of an installation-type information processing equipment like a desktop personal computer, a communication line is not always connected to this personal computer even when the owner has contracted to always on access. For example, when a user has both a desktop personal computer and a notebook-type computer, the user changes a connection of the communication line from the desktop computer to the notebook-type computer in many cases. In this case, the desktop personal computer is used as a standalone-type computer for using application like a word-processor software and a spread sheet software. The establishment of a communication path in this status also leads to a waste of power consumption, and this is not suitable either.